CFD Modeling of the Closed Injection Wet- Out Process For Pultrusion

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CFD Modeling of the Closed Injection Wet- Out Process For Pultrusion Michael Connolly Business Development Team Auburn Hills, MI, USA Mark Brennan Core

1 CFD Modeling of the Closed Injection Wet- Out Process For Pultrusion Michael Connolly Business Development Team Auburn Hills, MI, USA Mark Brennan Core Science Team Everberg, Belgium Huntsman Polyurethanes 9 th World Pultrusion Conference European Pultrusion Technology Association Rome, Italy March 27, 2008

2 Outline Definition of Process Challenge CFD Model Assumptions Equations Boundary Conditions Building Process Resin Flow Patterns Predictions of Pressure Profiles Comparison with Experimental Data Conclusions Future Work

3 Typical PU Pultrusion Set-up What is the box design? What is happening inside the injection box?

4 Process Challenge What is the internal design of the injection box? How can trial and error be eliminated/reduced? How can box design be optimized for particular parts and process conditions? Thick vs. thin Line speed Resin properties SOLUTION: Develop computational model Compare with detailed experimental work Validate and update model

CFD Model - Assumptions Micro-scale model of PU resin flow through fibers To model injection box at macro-scale we must use a phenomological approach Resin and

5 CFD Model - Assumptions Micro-scale model of PU resin flow through fibers To model injection box at macro-scale we must use a phenomological approach Resin and reinforcement represented as a moving porous medium (extension of Darcy s law) Surface tension effects captured by permeability tensor Single phase flow and constant viscosity

box porosity changes with position K z 1 Vf ( z) Gebart model of

6 CFD Model - Equations Navier-Stokes Equations u 0 2 u u p u S Source terms describing moving porous medium S u U K Injection box porosity changes with position K z 1 Vf ( z) Gebart model of permeability 2D c 2 3 f (1 ) 2 K x K y C D V 2 1 f f,max 1 4 (1 ) 5 2

7 Model Regions & Boundary Conditions Resin Inlet Rovings 1 p A A wet glass p inj 1 Rovings Entrance p p atm 0 Model Exit w W pull Initial Die Section die

8 Building a CFD model - 1 Build geometry

9 Building a CFD model - 2 Build Mesh

10 Building a CFD model - 3 Add Physics

11 Building a CFD model 4 Solve Simulation

12 Building a CFD model - 5 Look at Results

13 Resin Flow Patterns

14 Influence of Glass Fraction Pressure (barg) Glass = 50% Glass = 55% Glass = 60% Glass = 65% Superficial Velocity (m/min) Glass = 50% Glass = 55% Glass = 60% Glass = 65% Distance from die entrance (cm) Distance from die entrance (cm) Glass Fraction Glass = 50% Glass = 55% Glass = 60% Glass = 65% Permeability (m^2) Glass = 50% Glass = 55% Glass = 60% Glass = 65% Distance from die entrance (cm) Distance from die entrance (cm)

15 Influence of Glass Fraction Pressure rise quadratic with glass fraction z = 0 in. z = -1 in. z = -2 in. z = -4 in. More pronounced at die face than at transducer locations Pressure Rise (bar) Glass Fraction (-)

16 Pressure Rise in the Injection Box

17 Tapered Injection Box Setup Resin Injection Port (Top & Bottom) Digital Pressure Transducer at 5 cm from Die Face ROVINGS Tex PPG 2026 Digital Pressure Transducer at Tee Inlet Toggle Clamp and Mounting Bracket (with alignment pins)

18 Pressure Profiles in the Injection Box Pressure rises faster than model prediction

19 Comparison with Experiments Lower viscosity data Small variation with line speed Capillary forces now dominate? Simulation predictions lower than experimental data Rate of rise in pressure higher

20 Void Fraction Shorter Injection Box Higher Glass Fraction Resin Air Void %

21 Conclusions Model inputs include: Injection box geometry Number & location of ports Injection pressure Line speed Resin viscosity & density, glass fraction & density Permeability defined by glass fraction & flow direction Model outputs include: Pressure and velocity profiles Composite density Improvements needed: Improved permeability parameters Do additional experimental measurements Do small-scale flow modelling Add surface tension effects Consider encapsulation vs. filament wet-out

22 Future work Micro-scale modeling Surface tension effects Viscosity Experimental Permeability measurements Pultrusion trials New Materials CFM Engineered fabric New Geometries Thicker parts Round parts Consolidated wet-out Cure/Exotherm Mapping

23 2D Pultrusion Die Modeling

24 Die Exotherm: 6mm Thick Profile Zone 1 = 330 F (165 C) Temperature ( F) TC 1 TC 2 Injection box Cooling Zone 1 Zone 2 Cooling Exit of Die 12 IPM Core 18 IPM Core 24 IPM Core External 12 IPM External 18 IPM External 24 IPM Distance (in)

25 Cure/Exotherm Mapping: 6 mm Profile 18 IPM, Zone 1=330 F (45.7 cm/min, 165 C)

26 Questions???

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